1. Field of the Invention
This invention generally relates to a data reading machine and in particular to a facsimile machine having a contact type image sensor which is so structured to prevent water droplets from being formed by condensation.
2. Description of the Prior Art
Compact and handy data reading machines such as facsimile machines capable of being carried as connected to a belt placed around the shoulder of a human being or as mounted on a vehicle are becoming popular in the recent years, and these compact facsimile machines are used, for example, for transmitting instructions to delivery vehicles of package delivery services. Such hand-carry type facsimile machines are often used outdoors and experience an environment which is much worse in conditions than the environment which is encountered by ordinary facsimile machines which are used inside buildings, such as offices or at home. Thus, if such a handy facsimile machine is used outdoors, when the temperature of the environment in which the facsimile machine is placed changes abruptly, condensation could occur inside of the machine so that water droplets could be formed on various parts of the machine. When such condensation takes place, water droplets or dew are formed on a contact glass of an image reading optical system so that an original document could become stuck to the contact glass when brought into contact therewith to cause jamming of the original document. Depending on the amount of formation of water droplets on the contact glass, the original document is not properly transported over the contact glass or it becomes stuck to the contact glass to cause jamming. In the former case, the original image cannot be properly read by an image sensor, and in the latter case, the original document could be damaged.
It has been proposed to detect the occurrence of condensation or formation of water droplets by condensation in various machines, such as copying machines and facsimile machines. And, in accordance with the conventional scheme, when the occurrence of condensation has been detected, the entire system is halted until the water droplets thus formed by condensation inside a housing disappears, or a fan is driven to send the outside air into the machine, or a heater is activated to increase the temperature inside the machine. However, in the former case, an extremely long period of time is required, and in the latter two cases, extra components, such as a fan or heater, must be provided, which occupy an extra storage space inside the machine. Thus, these conventional schemes cannot be applied to handy facsimile machines because such handy facsimile machines require quick operation and do not have any extra space for such extra components.